Milk protein catches heavy metals To tackle the problem of heavy metal contamination in water, an ETH Zurich spin-off turns to whey. This byproduct of cheese production contains a cheap protein that makes for an effective water filter. Texte: Florian Fisch Infographie: ikonaut Produce a cheap water filter Heavy metals like arsenic or gold readily stick to proteins. Sreenath Bolisetty and Raffaele Mezzenga from the ETH Zurich found an abundant source of proteins in whey, the watery leftovers from cheese production. The most abundant whey protein (beta-lactoglobulin) grows into long fibers when heated. The researchers produce a thin paper-like membrane by adding cellulose, for holding everything together, as well as activated charcoal particles for retaining large molecules.
Membrane with customisable pores The protein fibres in the membrane remove over 99 percent of heavy metals. Its large pores let water pass through it without additional pressure, so the filter can be used in sewage water treatment. With a smaller mesh size, the membrane can also retain bacteria and viruses, which is necessary for water purification.
Recovery of precious heavy metals Once their protein fibres are fully covered by heavy metal atoms, the membranes have to be disposed of properly. Instead of being sent to the toxic waste deposit, they can be incinerated, which concentrates the heavy metals in the resulting ash. The filtering works for all the types of heavy metal tested. The spin-off BluAct commercializes the membranes for water purification and metal recovery. Its founders patented a method for producing gold nanoparticles and extracting other heavy metals. S. Bolisetty and R. Mezzenga: Amyloid–carbon hybrid membranes for universal water purification. Nature Nanotechnology (2016)
Horizons CC BY-NC